Does Retatrutide Make People Feel Hot, Sweaty or Cold? The Short Answer

Not according to its trials so far. Sweating, hot flashes, night sweats, fever, chills and feeling cold are not among the adverse events announced for any of retatrutide's five Phase 3 trials with results so far, and the text and tables of the full TRIUMPH-1 paper, published in September 2026, and of the Phase 2 obesity trial published in 2023 do not mention them. A less common effect cannot be ruled out, but there is no trial figure for it.

That does not mean the reports are imagined. Several things that are documented, or well known, can explain them: many products sold online as retatrutide are not the drug from the trials; a burning skin sensation, dysesthesia, was reported in every Phase 3 trial; heart rate rose in the trials; and eating much less can lower the body's heat production. Glucagon, the hormone behind retatrutide's third target, is the explanation most often given online, but it has not been shown to raise body temperature in people. Each explanation is set out below, with how strong the evidence for it is.

Why Some People Report Feeling Hot or Sweating

1. Many products sold as retatrutide are not the trial drug

Retatrutide is not approved and is not available by prescription. Lilly says it is legally available only through its clinical trials; in August 2026 it said it would also make it available to a limited number of patients who meet specific medical criteria and cannot enroll in a trial. Products bought online are not sold or supplied by Lilly.

The company warns that illicit retatrutide products "may contain unknown ingredients, harmful contaminants and impurities" and "may also have too much or too little active ingredient, or the wrong ingredient entirely." A June 2026 report by the consumer group Public Citizen counted 14 hospitalizations connected to retatrutide in the FDA's adverse event reporting system, and 14 FDA warning letters to companies selling it since 2024. Sweating, fever or chills after using one of these products cannot be assumed to be a retatrutide side effect.

Evidence: that these products are unregulated is well documented; how often they cause sweating or fever is not known.

2. Burning skin that feels like heat: dysesthesia

Burning skin is one of the ways people describe dysesthesia, an altered sense of touch. It was reported in all five Phase 3 trials with results so far: at the 12 mg dose, in 4.4% to 20.9% of participants depending on the trial, against 1.3% or less on placebo. The published TRIUMPH-1 paper labels the category "dysesthesia: skin burning sensation and related adverse events," and the Phase 2 trial had already reported related events, cutaneous hyperesthesia and skin sensitivity, in 7% of participants on retatrutide and 1% on placebo.

A 2026 pharmacovigilance study described skin burning sensations as a distinctive form of dysesthesia; in the French case reports it reviewed, which involved approved GLP-1-based medicines rather than retatrutide, the burning was mainly on the back, abdomen, thighs and arms. A burning sensation on the skin is not the same as a raised body temperature. The company describes the dysesthesia events in its trials as generally mild, or mild to moderate, and for most of the trials said the majority resolved during treatment.

Evidence: documented in the trials.

3. A faster heart rate

Heart rate rose on retatrutide in both published trials. In the Phase 2 trial it rose with the dose, by an average of about 9 beats per minute on 12 mg at 24 weeks on 24-hour monitoring, against less than 1 on placebo, and declined after that. In TRIUMPH-1, the mean pulse rate peaked at 20 weeks on 9 mg and 12 mg and decreased thereafter. The data are covered in why retatrutide increases heart rate.

Evidence: the rise in heart rate is documented; whether it contributes to feeling hot has not been studied.

4. The glucagon theory: what is and is not known

The glucagon receptor, retatrutide's third target, is the explanation most often given for feeling hot. Lilly says preclinical and early clinical data suggest retatrutide may promote maintenance of energy expenditure during weight loss. In early research, retatrutide increased energy expenditure in mice through the glucagon receptor, and the Phase 2 investigators speculated that glucagon receptor activation may augment effects on energy expenditure.

Burning more energy is not the same as running a temperature. In a 2016 study in 11 healthy men, an infusion of glucagon raised energy expenditure by 15%, about as much as cold exposure did. Unlike cold exposure, it did not raise the temperature measured over the lower neck, near the brown fat that cold activates, and no rise in brown fat activity was detected. That study used glucagon itself, not retatrutide, and Lilly's description of how retatrutide works does not mention body temperature.

Evidence: a plausible idea, not a demonstrated effect of retatrutide.

5. Low blood sugar

Retatrutide lowers blood sugar. Low blood sugar usually affects people with diabetes who take insulin or some other diabetes medicines, and its symptoms include sweating, shaking, feeling dizzy and heart palpitations. In TRANSCEND-T2D-1, where retatrutide was the only diabetes medicine, 3 of about 400 participants on retatrutide had blood sugar below 54 mg/dL, against none on placebo, and no one had severe hypoglycemia.

Evidence: documented, but uncommon in that trial.

6. Other common causes

Sweating and night sweats have many causes unrelated to any medicine. The NHS lists menopause hot flushes, anxiety, some medicines, low blood sugar, alcohol or drug use and hyperhidrosis, a condition that causes excessive sweating, as common causes of night sweats. It says night sweats should be checked by a GP when they happen regularly and wake a person up or cause worry; when they come with a very high temperature, feeling hot, cold or shivery, a cough or diarrhea; or when they come with unexplained weight loss.

Why Some People Feel Cold

Feeling cold, cold intolerance and chills are not among the adverse events announced for retatrutide's Phase 3 trials, named in the TRIUMPH-1 paper's text and tables or listed in the Phase 2 trial, so there is no retatrutide-specific evidence. One possible general explanation is eating much less.

In a six-month trial supported by the US National Institutes of Health and published in 2006, 48 overweight adults were randomized to a weight-maintenance diet or to one of three calorie-reduction approaches. Those who cut their energy balance by 25%, through diet alone or through diet plus exercise, had a lower average core body temperature at six months, and after accounting for changes in body composition, the energy their bodies used over 24 hours fell in all three calorie-reduction groups but not in the control group.

Retatrutide reduced appetite in its trials: decreased appetite was reported by 16.5% of TRIUMPH-1 participants on 12 mg, against 5.8% on placebo, and those on 12 mg lost an average of 28.3% of their body weight over 80 weeks if taken as intended (see TRIUMPH-1 results). Whether that lowers body temperature or makes people feel cold on retatrutide has not been studied.

Evidence: a known effect of eating less, not tested for retatrutide.

What Retatrutide's Trials Reported

Across the five Phase 3 trials, the adverse events the company's announcements list among the most common are nausea, diarrhea, constipation, vomiting and decreased appetite, along with upper respiratory tract infections, urinary tract infections, dysesthesia and, in TRIUMPH-3, hyperglycemia, which was more common on placebo. None of them is a temperature-related event. The company's more detailed medical-information summary of TRANSCEND-T2D-1 lists more than 20 adverse events, none of them temperature-related either. The full TRIUMPH-1 paper lists the adverse events reported by at least 10% of participants, which adds dizziness, dyspepsia, abdominal pain and fatigue, and a set of less common events of special interest such as low blood pressure; apart from dysesthesia, none involves temperature. The 48-week Phase 2 obesity trial's paper and appendix together list every adverse event reported by at least 5% of participants in any group, and none is sweating, flushing, fever or chills. The full side effect data are covered in retatrutide side effects.

One fever has been recorded in retatrutide research: in the first study of retatrutide in healthy volunteers, one of five people given a single 6 mg dose had a fever listed as related to the drug, a single case in a very small study.

Why This Page Has No Management Tips

Articles on this topic often suggest changing the injection day or the dose to manage feeling hot. This one does not: there is no trial evidence that retatrutide causes it, and retatrutide has no approved dose, so there is no approved way to adjust it.

Retatrutide and Body Temperature in Summary

Feeling hot, sweating and feeling cold are not side effects announced for retatrutide's Phase 3 trials so far, and the TRIUMPH-1 and Phase 2 papers do not name them. Possible explanations, each documented in its own right but not shown to cause these sensations on retatrutide, are products sold online that are not the trial drug, the burning skin sensation of dysesthesia, a higher heart rate and, for feeling cold, eating much less. The glucagon explanation is plausible but unproven: in one small study, glucagon raised energy expenditure without raising the skin temperature measured over brown fat. Common causes such as low blood sugar in people with diabetes, menopause and anxiety apply as well.

Sources

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• Eli Lilly. Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial. May 21, 2026.
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Medical Disclaimer: This article is for informational purposes only and is not medical advice. Retatrutide is investigational and is not approved by the FDA for any use. It is not available by prescription, and products sold online under its name are not sold or supplied by Lilly.